Ram Promaster 136 — Weekend Adventure Rig
van · 12V system · Fraser, CO
DIY Promaster 136 for weekend ski trips + summer mountain biking. 200Ah LiFePO4, modest loads, no A/C. Three days autonomy between recharges from the driving alternator + 200W rooftop solar.
Daily load
1,729 Wh
Daily Ah
144 Ah
Battery
600 Ah LiFePO4
Solar
600 W
Load budget
| Load | Watts | Qty | Hrs/Day | Wh/Day |
|---|---|---|---|---|
| 12V Cooler | 35 | 1 | 24 | 840 |
| Laptop | 60 | 1 | 3 | 180 |
| LED Cabin Light | 5 | 3 | 4 | 60 |
| Interior LED Strip | 12 | 1 | 4 | 48 |
| Roof Vent Fan | 15 | 1 | 6 | 90 |
| Freshwater Pump | 60 | 1 | 0.3 | 18 |
| Phone Charger | 10 | 2 | 2 | 40 |
| Heated Blanket | 60 | 1 | 4 | 240 |
| Diesel Heater Blower | 30 | 1 | 6 | 180 |
| Portable Radio | 3 | 1 | 3 | 9 |
| CO DetectorCRITICAL | 1 | 1 | 24 | 24 |
Battery bank
2 × 300Ah in parallel
Your daily consumption is 144Ah. With 3 days of autonomy, you need 432Ah of usable capacity. LiFePO4 (Lithium Iron Phosphate) batteries should only be discharged to 80% depth of discharge, so you need 540Ah of total capacity. We recommend a 600Ah bank (2 × 300Ah in parallel), giving you 480Ah of usable capacity — enough for 3 days without any charging.
Solar array
3 × 200W panels · 63A charge controller
Your daily consumption is 1729Wh. With 4.8 peak sun hours, a 75% system efficiency factor, and LiFePO4 (Lithium Iron Phosphate) round-trip efficiency of 96%, you need 500W of solar panels. We recommend 3 × 200W panels (600W total). This array will produce approximately 180Ah per day at 12V. You'll need a charge controller rated for at least 63A. MPPT recommended — higher efficiency at this array size.
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